The present invention relates to a chloroprene copolymer having remarkably improved resistance to oils, weathering, heat and freezing and to a process for producing the same.
Chloroprene rubber comprising a homopolymer or copolymer of chloroprene, i.e., 2-chloro-1,3-butadiene, has been used as an elastomer having most balanced physical properties in various applications.
However, the fact that the chloroprene rubber has well balanced physical properties means that each of the physical properties reaches the standard level but does not always mean that the individual physical properties are particularly excellent. Therefore, the chloroprene rubber is inferior to butadiene-acrylonitrile copolymer rubber in oil resistance, to ethylene-propylene copolymer rubber in weathering resistance, to chlorosulfonated polyethylene in heat resistance, and to natural rubber and polybutadiene rubber in coldness resistance.
For these reasons, in specific fields, chloroprene rubber cannot be used or it is giving way to other types of rubbers under the present circumstances.
On the other hand, improvements are being rapidly made on polychloroprene itself. For example, there are known DCR-50 as oil resistant polychloroprene, manufactured by Denki Kagaku Kogyo Kabushiki Kaisha, and DCR-34 as heat resistant polychloroprene, manufactured by Denki Kagaku K',ovs/o/ gyo Kabushiki Kaisha. Although there are proposed various chloroprenes in which a single property is improved as mentioned above, no chloroprene of the type in which all or most of the properties are improved has been developed. Moreover, improving one of the properties of the chloroprene often leads to a deterioration of the other properties. For example, the low temperature brittle points of the above-mentioned DCR-50 and DCR-34 are rather higher than that of conventional polychloroprene.